1. Field of the Invention
The present invention generally relates to an apparatus incorporating therein opposing two members and a spring element or elements interposed therebetween for converting a reaction force of the spring element that generates when the two members are moved toward or away from each other by an operation force applied to the two members from the outside, to a different type of force enabling the apparatus to exhibit a novel working function. More particularly, the present invention relates to a spring reaction force converting apparatus of the above-described configuration, which is capable of converting the reaction force of the spring to a different type force transmitted to the two members through a link mechanism during applying of an operation force to the two members, thereby reducing the operation force applied to the two members gradually from a large value at its initial time to a smaller value at a time of termination of application.
2. Description of the Related Art
Hitherto, an IC socket for use in connecting an electronic part such as an IC package to a circuit substrate has been constructed to include: a mount on which an electronic part or parts is mounted; a socket main body on which the mount is securely mounted; a cover member provided to be vertically movable with respect to the socket main body; a pressure applying mechanism for holding the electronic part or parts mounted on the mount; and a plurality of electric contacts to be connected to the electronic parts. The pressure applying mechanism has a pressure applying lever supported to be rotatable with respect to the socket main body and the socket main body is provided with two or four coil springs disposed to push up the cover member (see for example, Japanese Laid-open (Kokai) Patent Application Publication No. 2003-332010).
The socket main body and the cover member of the above-mentioned IC socket can be typically illustrated as shown in FIG. 9, in which a cover member 2 is disposed to be vertically movable above the socket main body 1, and two coil springs 3a, 3b are provided between both the socket main body 1 and the cover member 2 at both ends so that the cover member 2 is urged upward by the coil springs 3a, 3b. Thus, when the cover member 2 is pushed down against the elastic force of the coil springs 3a, 3b, activation of the pressure applying lever of a pressure applying mechanism (not shown in the figure) occurs.
However, in such a conventional structure of the socket main body and the cover member, when an operation force F is applied downwardly from above the cover member 2 as indicated with an arrow, with the socket main body 1 mounted on the circuit substrate 4, the cover member 2 is lowered so that the coil springs 3a, 3b are contracted and a reaction force R directed upward is generated by the coil springs 3a, 3b as indicated with arrows. At this time, the coil springs 3a, 3b are directly connected at opposite ends thereof to the socket main body 1 and the cover member 2 in a condition where these coil springs are arranged perpendicularly to the socket main body 1 and the cover member 2, so that the downward directed operation force F to the cover member 2 and the reaction force R of the coil springs 3a, 3b act toward opposite directions while opposing each other.
With such a state, as the cover member 2 is pressed further, the reaction force R of the coil springs 3a, 3b increases and as the pressing of the cover member 2 is released, the reaction force R of the coil springs 3a, 3b decreases. In this case, as the cover member 2 is lowered, the operation force F applied from above to the cover member 2 increases and as the cover member 2 is raised and upwardly moved, the operation force F applied to the cover member 2 decreases. In other words, in an operation of mounting the electronic part or parts on the mount of the socket main body 1, in an initial period of pushing down the cover member 2, the operation force F is small and feeling of the operation for applying the force F is sensed by an operator to be light, and in the period of termination of mounting the electronic part by pushing down the cover member 2, the operation force F increases and the feeling of the operation is sensed by the operator to be heavier. Therefore, as a whole, the operability is poor.
With the electronic part or parts mounted on the mount of the socket main body 1, the cover member 2 is upwardly moved, so that the mounted electronic parts are held as they are by a pressure application lever of the pressure applying mechanism. At this time, as the cover member 2 is upwardly moved to be further raised above, the reaction force R of the coil springs 3a, 3b decreases, and as a result, holding of the electronic parts by the pressure application mechanism must be weakened.